Engines, including diesel engines, gasoline engines, gaseous fuel powered engines, and other engines known in the art ignite injections of fuel to produce heat. In one example, fuel injected into a combustion chamber of the engine is ignited by way of a spark plug. Specifically, a high voltage current is directed through an electrode located at a center of the spark plug, from a terminal end to a distal free end. The distal free end is spaced a particular distance from a grounded portion of the spark plug such that an arc spanning from the distal free end to the grounded portion is generated. This arc has sufficient voltage to breakdown and thereby ignite an air and fuel mixture within the combustion chamber.
Although successful at initiating combustion, conventional spark plugs suffer from low component life. That is, the associated high breakdown voltage requirement of the spark plug's arc can be damaging to the grounded portion of the spark plug. Over time, the grounded portion may become pitted at the arc termination location and, thereby, change the distance between the electrode and the grounded portion. As this distance increases, arcing reliability is reduced and the spark plug should be replaced to ensure continued operation of the engine.
One attempt at extending the life of a spark plug is described in U.S. Pat. No. 1,268,322 (the '322 patent) issued to Clark on Jun. 4, 1918. The '322 patent discloses a spark plug having a stem electrode with a distal free end located within an integral thimble electrode. A predetermined gap spacing is maintained between the distal free end and an axial end of the thimble electrode by rotating the stem electrode relative to the thimble electrode. As the stem electrode is rotated, it advances axially into the thimble electrode, due to threading of the stem electrode. The stem electrode is advanced until it engages the axial end of the thimble electrode, thereby dislodging any soot or oil built up at the axial end of the thimble electrode or at the distal free end of the stem electrode. After the soot or oil is dislodged, the stem electrode is rotated in a reverse direction to separate the distal free end from the axial end by the predetermined gap spacing. The threading on the stem electrode is of convenient pitch such that a technician may set the gap spacing by turning the stem electrode through a certain number of revolutions.
Although the spark plug of the '322 patent may have extended life compared to non-adjustable spark plugs, it may still lack reliability, applicability, and accuracy. That is, even though oil and soot may be dislodged and the stem electrode may be maintained at the appropriate distance from the axial end of the thimble electrode, the gap spacing may not account for pitting. That is, if pitting occurs at the axial end, the technician may have no way of knowing to what angle the stem should be rotated to avoid arc termination at the same pitting location, as only the spacing from the axial thimble wall is of concern in the '322 patent. And, the adjustment method of the '322 patent may not be applicable to spark plugs with stem electrodes that have radially oriented prongs, where the arc terminates at an annular side wall of the pre-chamber. Further, even though threading of the spark plug disclosed in the '322 patent may be convenient, it may provide opportunities of inaccuracies in stem electrode placement.
The igniter of the present disclosure solves one or more of the problems set forth above.